Submission to CRAN

After all the groundwork of the previous weeks, awkreader was finally in fighting shape for its CRAN debut. The vignette was polished, the new methods (record.count and aggregated.fread) were documented, and we had a shiny new suite of parameters (delim, skip, file.pattern) to show off.

With everything pushed to the repo, I took a deep breath and hit the “CI checks” button. There’s no sweeter mix of relief and terror than watching the badges turn green or red.

Linux? Passed. Mac? Passed.

Windows? …Of course it didn’t.

It wouldn’t be an R package submission without at least one sacrificial offering to the Windows gods.

The Failure (A Classic)

The error logs pointed a glaring finger at helpers.R while building the vignette, specifically this line:

# Count records in all CSV files in the data directory
combined.fread(the.files = data.path, file.pattern = "*.csv")

My immediate suspect was quoting. Surely, a rogue space in a file path was breaking the awk command. I went on a quoting spree: shQuote everywhere, double quotes, single quotes, you name it. Still red.

I even tried the old “8.3 short filename” trick (shortPathName()) to dodge spaces. It turns out that was a complete dead end: modern Windows Server CI images frequently disable 8.3 generation for performance, meaning shortPathName() just silently hands back the long path without any warning. A classic Windows booby trap.

After staring at the failure for far too long, I realized the truth: it wasn’t a space in the path. It was a hostile takeover of the shell.

Plot Twist: The Shell Hijack

fread(cmd = …) doesn’t execute commands directly. On Windows, it hands the string off to R’s shell() function. shell() checks R_SHELL, then SHELL, and only falls back to COMSPEC (cmd.exe) if neither is set. On the GitHub Actions runner, SHELL was pointing squarely at Rtools’ bash.exe, a necessary evil for compiling source packages during the build process.

Here’s where things went off the rails: normalizePath() on Windows happily returns paths with backslashes, like:

C:\rtools45\usr\bin\awk.exe

That’s perfectly legible to cmd.exe. But to bash? It’s complete gibberish. Bash treats backslashes as escape characters and the colon as a path separator in the context of a drive specifier. It had absolutely no idea what C:\rtools45... was supposed to mean and immediately threw exit code 127, the dreaded “command not found” error.

Better quoting wouldn’t have saved me, because the binary name itself was unparseable in that shell’s syntax. I wasn’t fighting a quoting bug; I was fighting a fundamental mismatch between how Windows paths are represented and how a POSIX shell interprets them.

The fix wasn’t cosmetic; it was structural. I forced shell() to skip bash entirely by temporarily unsetting SHELL and R_SHELL, ensuring it fell back to cmd.exe:

if (is.windows) {
  old.shell  <- Sys.getenv("SHELL",   unset = NA)
  old.rshell <- Sys.getenv("R_SHELL", unset = NA)
  Sys.unsetenv("SHELL")
  Sys.unsetenv("R_SHELL")
  on.exit({
    if (!is.na(old.shell))  Sys.setenv(SHELL = old.shell)
    if (!is.na(old.rshell)) Sys.setenv(R_SHELL = old.rshell)
  }, add = TRUE)
}

This forced shell() to fall through to COMSPEC (i.e., cmd.exe). The AWK binary finally ran without complaint.

…Except now, Windows decided to hit me with its other favorite limitation.

The Second Punch: Command Line Length

With cmd.exe finally in charge, I hit a brand-new wall. Windows has a hard-coded command-line length limit of 8,191 characters. My command, passing hundreds of CSV files at once, was clocking in at nearly 18,000 characters.

I was essentially asking cmd.exe to swallow a full sandwich in one bite. It choked immediately.

The fix was to stop relying on the user to set num.files.per.batch correctly and instead make the function self-aware. I added a dynamic chunking system that splits each batch into sub-chunks:

file.chunks <- list()
current <- character(0)
current.len <- fixed.prefix.chars
for (f in norm.batch.files) {
  f.len <- nchar(f) + 3L
  if (length(current) > 0 && (current.len + f.len) > max.cmd.chars) {
    file.chunks[[length(file.chunks) + 1]] <- current
    current <- character(0)
    current.len <- fixed.prefix.chars
  }
  current <- c(current, f)
  current.len <- current.len + f.len
}
if (length(current) > 0) file.chunks[[length(file.chunks) + 1]] <- current

chunk.cmds <- vapply(file.chunks, run.chunk, character(1))
awk.statements[i] <- paste(chunk.cmds, collapse = " && ")

Now, regardless of the original batch size, the function automatically splits the file list into sub-chunks that respect the 7,000-character safety limit and chains them together with &&.

The Sweet Victory

With both fixes in place, the Windows build turned green faster than I could refresh the page.

All checks passed. No errors. No warnings.

awkreader will shortly be officially going live on CRAN!

Key Takeaway Cross-platform R development isn’t just about writing portable R code; it’s about understanding how your functions interact with the underlying OS, shell environments, and system-level limitations. The same function that works flawlessly on your local machine can unravel in surprising ways on a CI runner with a different SHELL environment variable or a stricter command-line limit.

If there’s one thing this experience taught me, it’s this: don’t assume. Test on Windows. And when it fails, question not just your code, but the entire execution environment.

Give It a Spin

awkreader will shortly be live on CRAN. Install it with:

install.packages("awkreader")